Pawl-and-ratchet device



(No Model.) I 2 Sheets-Sheet 1.

A. B. GASE.

PAWL AND RATGHET DEVICE.

No. 435,087. Patented Aug. 26, 1890.

, P1 5 Fig.7

(No Model.) 2 Sheets-Sheet 2.

A. B. CASE. PAWL AND RATGHET DEVICE.

No. 435,087. Patented Aug. 26, 1890.

UNITED STATES PATENT OFFICE.

ADELBERT B. CASE, OF SPRINGFIELD, MASSACHUSETTS.

PAWL-AN D- RATCH ET D EVlC E.

SPECIFICATION forming part of Letters Patent No. 435,087, dated August 26, 1890*.

Application filed June 18,1890. Serial No. 355,897. (No model.)

To alZ whom it may concern:

Be it known that I, ADELBERT B. CASE, of Springfield, in the county of Hampden and State of Massachusetts, have invented a new and useful Improvement in Pawl-and-Ratchet Devices, of which the following is a specification, reference being had to the accompanying drawings, forming part thereof.

My invent-ion relates to that class of pawl- [O and-ratchet mechanisms in which a pawl operatively connected with and carried by a shaft cooperates with ratchet-teeth upon the inner surface of a hub embracing said shaft, to cause said shaft and hub to revolve in uni- I 5 son in one direction, and to permit the shaft to revolve independently of the hub in the opposite direction; and the invention has especial reference to such mechanism as applied to lawn-mowers to make the connection between the shaft carrying the wiper-knives and the pinion-gears, through which motion is transmitted from the draft-wheels to saidshaft. It is a fact well known to those who have occasion to use lawn-mowers that the part which sustains the greatest wear in such machines and which soonest requires to be repaired or renewed is the connection between the wiper-shaft and its operatingears. Vt ith a view. to overcoming this objection inside pawlandratchet mechanisms have been largely adopted, said mechanisms comprising an annular recess in the bore of the piniongears, located midway between the ends of said bore, with ratchet-teeth extending into said recess from one or both sides thereof, and a pawl located within a longitudinal groove in the shaft and having a free sliding movement therein, which pawl, by its en- 0 gageinent with said ratchet-teeth in the gear, causes the latter and the shaft to revolve in unison in one direction and permits the gears to revolve independently of the shaft in the opposite direction. Various forms of pawls and ratchets to be thus used have been devised, but in all of them a single pawl is utilized to co-operate with either one or two rows of teeth. In the former casethat is to say, when the single pawl is used with a single row of ratchet-teeth -the maximum amount of lost motion resulting from areversal of the movement of the machine is of course the distance between the individual teeth of the series, and as but three teeth are usually employed such lost motion is considerable and the wear upon the teeth and pawl very rapid. In the latter case, with two rows of teeth and those of one row alternating with those of the other, the amount of lost motion is reduced one-half; but even in such case the single pawl is rapidly worn to such an extent as to seriously impair its perfect engagement with the teeth. In either case, more over, the leverage of the pawl upon theteeth being located wholly upon one side of the longitudinal center of the hub of the piniongear, a torsional strain upon said hub is exerted, which wears the bore thereof in such manner as to in time cause a looseness in the movement of the gear and an imperfect operation of the wiper-knives. I have found that these and other objections to such previous constructions can be entirely obviated by employing, .in connection with one or two rows of inside ratchet-teeth on the piniongear, a plurality of pawls on the shaft to engage said teeth, said pawls being located at circ um ferentially-different points of the shaft; and my invention therefore consists of such combination and arrangement of said parts,

as hereinafter fully described, and particularly pointed out in the claims.

Referring to the drawings, in which like letters designate like parts in the several figures, Figure 1 is a central longitudinal section of a hub and shaft provided with a pawland-ratchet mechanism embodying my invention. Fig. 2 is a similar view of the hub detached from the shaft. Fig. 3 is a diagram illustrating the contour of the internal annular recess of the hub. Fig. 4 is a view in per spective and longitudinal section of the shaft and pawls. Fig. 5 is a cross-section of a shaft provided with three pawls. Fig. 6 is a diagram similar to Fig. 3, illustrating the appli cation of my invention to a hub having two rows of ratchet-teeth. Fig. 7 is an end view of the shaft designed to be used with said last-mentioned form of hub. t

The letter a designates a shaft, and b a hub revolubly mounted thereon, which may be the hub of a pinion-gear as utilized to operate the wiper-shaft of a lawn-mower, or of any other form of wheel which is designed to drive or to be driven from the shaft (1. Midway between its ends said hub 11 is provided with an internal annular recess b, into which project ratchet-teeth 11 As shown in Figs. 1, 2, and 3, said hub is provided with three of such teeth located at equal distances apart and upon the same side of the recess b,

while upon the opposite side of the recess and alternating with said teeth are projections b the office of which is to facilitate the proper engagement of the pawl with the teeth, as clearly described in Letters Patent No. 383,624., granted to me May 29, 1888.

The shaft (1 is provided with two longitudinal grooves a, which, as shown in Figs. 1 and 4, are located at diametrically-opposite points, and which receive the bases 0 of two pawls c in such manner as to permit a free sliding movementof the latter within said grooves. The pawls c are preferably provided with one flat and two curved faces to enable them to ride freely over the teeth 19 of the hub when the latter is revolved in one direction, and to make a firm engagement with said teeth when the hub is revolved in the opposite direction, as fully explained in my said previous Letters Patent. In the construction shown and described in my said Letters Patent, however, but a single pawl is employed, and some of the more serious objections incident thereto are hereinbefore specified.

By reference to the diagram shown in Fig. 3, in which the position of the two pawls relatively to the three teeth of the hub is illustrated, it will be observed that when one pawl is. in operative engagement with one tooth the other pawl is midwaybet ween two teeth, and consequently that the maiimum amount of possible lost motion even with a single row of teeth is but one-half the distance between two teeth, thus reducing the force of theimpact of the teeth with the pawls upon a reversal of the movement of the hub by one-half. One of the main causes of the rapid wear of both teeth and pawl in previous constructions is thus obviated. Moreover, the alternate action of the two pawls upon the teeth distributes the wear between the former in such manner as to more than double the effective life thereof. The results just mentioned are due to the relative arrangement of the three teeth on the hub and the two pawls located at diametrically-opposite points on the shaft. It is obvious, however, that by employing a greater number of teeth on the hub, or by varying the relative positions of the grooves in the shaft, the two pawls can be made to operatively engage two teeth simultaneously instead of alternately. Such an arrangement would secure a stronger engaging action between the shaft and hub, and would materially reduce the wear of both teeth and pawls, as compared with previous constructions; but as. the amount of lost motion would not be reduced I prefer to employ the arrangement of said parts first described.

It is obvious that more than two pawls can be utilized in the manner described to produce very beneficial results, and I have shown in Fig. 5 a shaft provided with three grooves and three pawls located at equal distances apart therein, which, if used in connection with the hub represented in Fig. 3,would cause the three pawls to engage the three teeth simultaneously, thereby securing an exceedingly strong engagement of the hub with the shaft, which can be used to great advantage in the larger sizes of lawn-mowers and in other heavy machinery. Whatever number of pawls be employed, their relative action upon the teeth of the hub can in each instance be accurately predetermined by the relative circumferential locations of the grooves a" in the shaft.

While, as thus far described, my invention secures very important advantages as applied to a hub having ratchet-teeth upon one side of the annular recess therein, it is equally applicable to hubs having teeth upon both sides of its recess, as represented by the diagram shown in Fig. 6. In this case the teeth upon one side of the recess b alternate in position with those upon the opposite side thereof, and the pawls c arelocated within the diametrically-opposite grooves a of the shaft a, (shown in Fig. 7,) said pawls preferably being provided with right and left hand working-faces, and having their bases extending in opposite directions.

In this application of my invention I not.

only secure all of the advantages hereinbefore enumerated, but I also secure the additional one of dividing the strain upon the hub equally upon opposite sides of the longitudinal center thereof, and thus obviate the torsional strain which results from the engagement of a single pawl with a tooth at one side of said center, and which is the cause of very rapid wear of the hub.

The advantages specified incident to the use of a-plurality of pawls are equally apthe former drive the latter, because of the 'by elfect a material saving in the outlay required for repairs and renewal of worn-out parts.

While I have shown and described my invention in connection with sliding pawls, it is obvious that it can be applied to the various other forms of pawls which have been de-- vised to co-operate with inside ratehet-teeth upon a hub, Having thus fully described my invention,

described, comprising a hub bored centrally to receive a shaft, and provided with an internal annular recess and with ratchet-teeth projecting into said recess in a plane substantially parallel with the axis of said hub, in combination with a shaft adapted to occupy the bore of said hub, said shaft having movably connected therewith at dilferent points thereof circumferentially a plurality of paWls adapted to operatively engage said ratchetteeth on the hub, arranged and operating substantially as set forth.

3. The combination, with a hub having a central bore, an internal annular recess, and ratchet-teeth projecting Within said recess, as

described, of a shaft adapted to fit the bore of said hub, said shaft being provided with a plurality of peripheral grooves extending parallel with the axis thereof,and with a sliding pawl locatcd within each of said grooves and projecting beyond the circumferential plane of the shaft, whereby said pawls are adapted to operatively engage the ratchetteeth on said hub, substantially as and for the purpose described.

4. The combination, with a hub having a central bore to receive a shaft, an internal annular recess located midway between the ends thereof, and a series of ratchet-teeth projecting into said recess from one side thereof, of a shaft having two longitudinal grooves therein located at diametrically-opposite points thereof, and two paWls having their bases located Within said grooves, respectively, and adapted to have a sliding movement therein, said pawls projecting beyond the circumferential plane of said shaft, whereby they are adapted to operatively engage said teeth on the hub, substantially as described.

ADELBERT B. CASE. WVitnesses:

W. H. CHAPMAN, J. E. CHAPMAN. 

